In downlink transmission of a 3GPP LTE-advanced (LTE-A) system, both a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH) are configured a transmission mode of transmit diversity. With such wireless transmission channels, the system may obtain a diversity gain to improve the receiving performance.
For the LTE-A system, a main processing flowchart of the transmit diversity in a physical layer is shown in FIG. 1. Information bits are encoded by an encoder to form codewords, then the codewords are sequentially subjected to scrambling and modulation mappers to form transmitting symbols, and then the transmitting symbols are sequentially subjected to a layer mapper and precoding, a transmission mode may be configured via the precoding into a transmit diversity mode; and at last, after resource mapping and orthogonal frequency division multiplexing (OFDM), modulated signals are sent out from a plurality of transmitting antenna ports.
Accordingly, a processing flowchart at a receiving end is shown in FIG. 2. Received signals are sequentially subjected to OFDM demodulation, resource demapping, channel estimation, processing of a transmit diversity processing unit, layer demapping, demodulation and decoding; and at last, the information bits are output.
In the LTE-A, particularly for the sake of supporting a complex interference environment in a heterogeneous network in a version Release 11, an IRC technology is generally adopted by a receiver so as to cope with strong interference of neighboring cells. A conventional method is the minimum mean square error-IRC (MMSE-IRC) stated in a technical report of the 3GPP. However, to support multiple input multiple output (MIMO) transmission on more than two layers in the LTE-A, up to 4 receiving antennas may be provided. In this case, according to the conventional MMSE-IRC processing, the IRC needs to perform inversion of an 8-8 matrix, and thus the processing of the receiver is very complicated.